I keep forgetting what to do to add the Firefox 4 beta to my Ubuntu Linux 10.04 Lucid systems. It’s quick and easy, just copy the lines below (one at a time) into Terminal and add the PPA sources to Apt. Then Minefield browser will be installed as the pre-packaged version of the Firefox 4 beta.
sudo add-apt-repository ppa:ubuntu-mozilla-daily/ppa
sudo apt-get update
sudo apt-get install firefox-4.0